Get pose from bones that get motion from parent objects
You need to Bake the pose into an Action using visual keying:


Pose > Animation > Bake Action
You can bake 1 frame by setting the start and end to the same frame
Set Visual Keying ON
Set Clear Constraints ON
Set Clear Parents ON
Bake Data to Pose


Now you should have an action with desired pose keyed.

You can load this action into Pose library (make it suitable for pose library with help ring icon)